Dissertation (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The kinetics of drying and film formation of different polymeric latices were studied.
Various theoretical models predict a strong dependency of the film formation
characteristics on the particle size and morphology. This could be confirmed by
experimental studies.
The influence of particle size and morphology of differently structured latices on the
film formation process was investigated by Atomic Force Microscopy (AFM) and
Ultrasonic shear wave reflection. These two methods allow a comprehensive
characterization of the drying and film formation process of emulsions. The studies
confirmed the theoretical model, that the film formation behavior is influenced by the
particle size and particle morphology.
Furthermore the influence of different additives, such as coalescent solvents and
rheology modifiers on the film formation behavior was investigated.
As a second part of the studies, a novel technique was developed to measure
thermal transitions of polymers with the AFM in the non-contact mode, using it as a
Dynamic Mechanical Analyzer (DMA) on a local scale. The resonance frequency of
the AFM cantilever was measured as a function of the temperature and thermal
transitions of a polymer were clearly visible as changes in the resonance frequency /
temperature response curve. Using the AFM in this mode allows the determination of
the thermal properties of a material at a specific position on a sample, thereof on a
macromolecular scale. A simple model was developed to explain the response of the
cantilever caused by the transitions in the polymer and the related form of the
frequency/temperature curves.
This new technique adds a new dimension to standard thermal analysis techniques.
It is now possible to resolve the individual thermal transitions of different polymer
phases, for example in structured multiphase polymers. / AFRIKAANSE OPSOMMING: Die kinetika van droging en filmvorming van verskeie polimeriese lateksverbindingse
is ondersoek. Verskeie teoretiese modelle voorspel 'n sterk afhanklikheid tussen die
filmvormingseienskappe, partikelgrootte en morfologie. Hierdie afhanklikhede is
eksperimenteel bevestig. Die invloed van partikelgrootte en morfologie van
verskillende lateksstrukture op die filmvormingsproses is deur
atoominteraksiemikroskopie (Eng: Atomic Force Microscopy, AFM) sowel as
ultrasoniese skuifweerstandgolfrefleksie ondersoek. Hierdie twee metodes bied 'n
deurslaggewende karakterisering van die droging en filmvormingsproses van
emulsies. Resultate bevestig die teoretiese model, nl. dat filmvorming deur
partikelgrootte en morfologie beïnvloed word.
Die invloed van verskillende bymiddels, insluitend reologie-modifiseerders op
filmvorming, is ook ondersoek.
Vervolgens is 'n nuwe tegniek ondersoek om die termiese oorgange van polimere
met behulp van die AFM in nie-kontak modus (deur dit as 'n dinamiese meganiese
analiseerder (DMA) te gebruik) te bestudeer. Die resonansie-frekwensie van die
AFM-hefboom is bepaal as 'n funksie van temperatuur. Termiese oorgange van 'npolimeer is duidelik waarneembaar as veranderinge in die resonansfrekwensie/
temperatuur responskurwe. Deur gebruik te maak van die AFM in hierdie
modus kan die termiese eienskappe van 'n materiaal by 'n spesifieke posisie op die
monster op molekulêre skaal bepaal word. 'n Eenvoudige model is ontwikkel om die
oorgange in die polimeer, en gevolglik die vorm van die frekwensie/temperatuur
kurwes, dmv. die respons van die hefboom, te verduidelik
Hierdie nuwe tegniek gee 'n nuwe dimensie tot die standaard tegnieke van termiese
analise tegnieke. Dit is nou moontlik om individuele termiese oorgange van verskeie
polimeerfases, byvoorbeeld in gestruktureerde multifase polimere, te ondersoek en
op te los
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52847 |
| Date | 03 1900 |
| Creators | Meincken, Martina |
| Contributors | Sanderson, R. D., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 125 pages : illustrations |
| Rights | Stellenbosch University |
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